The notion that feminists are trying to change the way we think about things by changing language is all well and good, I suppose. I quote directly from another node when I say, "To be able to change the world, we have to change the way we think of it." I'm fine with that, and I love attempting to solve problems by looking at them from a different perspective or putting a twist on them or spelling them differently.
Here is the problem with it, though, as I see it. Womyn isn't really a new word; it's a new spelling. We're not changing language when we spell words differently (1337 speak included); we're just ... spelling words differently. In conversation, we're not even really changing the way we think about woman, since one cannot discern differences in spelling through speech (I think). As an exercise, try saying the two words aloud, first "woman" and then "womyn". Use the word "womyn" in a conversation, and then ask your partner if they could tell that you were substituting "womyn" for "woman" in an attempt to change the way we think about gender relationships. If s/he could tell, then good for both of you; but I'm willing to bet that s/he did not notice that you were changing the way you (pl.) think about the world so that you (pl.) could change the world.
That's why I don't think "womyn" means anything. To reiterate, it's not really a new word, merely a new spelling. And as great as things are on paper, they often do not work out in the real world.
If spelling could change the world, I'd start referring to him as George W. Busch just to see if the newly-spelled president was any better than our currently-spelled president.